1. Field of the Disclosure
The present disclosure relates to a decorative film for decorating the surface of a resin molded product, and also to a molded product including the decorative film. In particular, the present disclosure relates to a decorative film that hardly causes the ink to bleed, which may conventionally occur in a colored layer formed by an ink-jet printer.
2. Background Art
In recent years, in-mold decorative films have been commercially available, which include colored layers printed by an ink-jet printer in order to create various designs and patterns. This type of decorative films does not need plates for printing, which results in a low cost and a short lead time and is also suitable for on-demand printing of high-mix, low-volume products.
It has been proposed to use ultraviolet (hereinafter, UV) curable inks for these decorative films because they can dry and cure much faster than water- and solvent-based inks.
FIGS. 8A to 8C show the configuration of an ink-jet printer with UV curable ink. FIG. 8D is a sectional view of a conventional partial layer film, which is printed by this printer.
In the printer, supply reel 300A is wound with partial layer film (hereinafter, film) 400, which is a continuous film. As shown in FIG. 8D, film 400 includes base film 401, which is, for example, a PET or acrylic film. Release layer 402, protective layer (also called, the hard coat layer) 403, and anchor layer 407 are formed in that order on base film 401. Film 400 is wound around supply reel 300A in a manner that base film 401 is located inside and anchor layer 407 is located outside.
Film 400 is rolled out from supply reel 300A, fed over stage 303 in the direction from Y3 to Y4, and taken up on take-up reel 300B. Stage 303 suctions air to fix film 400 thereon so as to be in print position.
As shown in FIGS. 8A to 8C, above stage 303, the printer includes ink-jet head (hereinafter, head) 301 and UV lamp unit 302, which cures ink ejected from head 301 and landed on anchor layer 407. Head 301 includes a plurality of heads for different colors, and these heads are arranged in the X1-X2 directions crossing the direction to transfer film 400 (from Y3 to Y4). When head 301 and UV lamp unit 302 move from X1 to X2 over film 400, ink ejected from head 301 is printed on film 400. When head 301 and UV lamp unit 302 return from X2 to X1, UV lamp unit 302 cures the UV ink landed during the travel from X1 to X2 with UV light. When the printing for one line is completed, head 301 and UV lamp unit 302 move from Y3 toward Y4 to repeat the printing operation.
When this operation is over, stage 303 releases film 400 from suction. Take-up reel 300B takes up film 400 with an arbitrary length in the direction from Y3 to Y4 so as to include portions where the colored layer has not been formed yet.
This type of ink-jet printing is called a multi-pass type. In this type, the colored layer is formed on the surface of anchor layer 407, but the printing speed is as low as 0.1 m/min or less on an average, indicating poor productivity.
In recent years, single-pass ink-jet printers, which are free from this problem, have been commercially available. FIGS. 9A and 9B show the configuration of a single-pass ink-jet printer.
Unlike in the multi-pass type, in the single-pass type, ink-jet head (hereinafter, head) 501 and UV lamp unit (hereinafter, unit) 502 are in the fixed position while film 400 is being fed from Y5 toward Y6 in order to be printed.
More specifically, supply reel 500A and take-up reel 500B control film 400 to be continuously fed from Y5 toward Y6 in order to be printed. The printer further includes cylindrical stage 505, which is composed of rotating cylindrical rollers and is disposed under head 501 so that film 400 can be fed smoothly. Film 400 is not fixed by air-suction by stage 505, but is fed with an arbitrary tension applied thereto.
Head 501 includes a plurality of nozzles for each color. The nozzles for the same color are arranged in a direction crossing the Y5-Y6 directions within the print width of film 400. The nozzles for different colors are parallel-arranged in the Y5-Y6 directions. Head 501 includes an arbitrary number of heads depending on the print width, the image resolution, and the number of ink colors required.
In this configuration, UV curable ink 601 is ejected onto film 400 continuously being fed under head 501, thereby forming colored layer 504 with arbitrary images printed thereon. Then, unit 502 in the downstream of head 501 applies UV light to colored layer 504 to photo-cure (polymerized) it, and hence, a decorative film is completed. This decorative film is then taken up on take-up reel 500B.
The single-pass type can print at a speed as high as 20 m/min or more, indicating much higher productivity than the multi-pass type.